Chevy Small-Block Perfection

What’s your dream engine? A big-block Chevy? A 426 Hemi? A supercharged LS9? When was the last time you longed to own a 358ci small-block Chevy? We know, it’s been a while -- but that’s about to change.

Since 1974, Chevrolet has been running a 358ci V8 in NASCAR’s Sprint Cup series. Chevrolet’s latest NASCAR race engine, known as the R07, which debuted in 2007 is perhaps the most refined small-block in the world.

The R07 shares few similarities with any production small-block in your driveway. It’s become a purpose-built engine, no longer based on any street engine. “It’s a departure from the Small-Block, Generation 2 (SB2) race engine, the R07’s predecessor, which was a direct evolution of the Chevrolet small-block,” says Pat Suhy, NASCAR Engineering group manager with Chevrolet.

“The SB2 was very much like a small-block, with a 9-inch deck height and flooded water jackets.” During the SB2’s reign, race engines had to resemble engines on dealership floors, but they didn’t have to share any of the parts. The R07 engine doesn’t even have to look like a production engine.

This is a “revised V8, the natural evolution,” says Dr. Andy Randolph, engine technical director at Earnhardt-Childress Racing (ECRengines.com). NASCAR has stayed with the pushrod small-block V8 design, while global racing series like F1 have more open engine rules. For those who say F1 has the most advanced engines in motorsports, let’s put things into perspective: According to EPI Inc. (EPI-eng.com) -- a company that designs and develops piston engines for everything from race cars to airplanes -- an F1 2.4L V8’s peak piston speed is 8,349 feet per minute at 18,000 rpm, while a Sprint Cup’s engine peak piston speed is 8,780 feet per minute at 10,000 rpm. It takes serious engineering to make an engine last 600 miles with that piston speed.

While small-block NASCAR engines have retained the same basic principles since 1955, the past six years have seen huge rule changes. In 2011, NASCAR dropped unleaded hydrocarbon fuel for E15 (15 percent ethanol, 85 percent gasoline) fuel, and teams switched to electronic fuel injection (EFI) in 2012. From a technical standpoint, EFI brought about an entirely new way of looking at the sport, with the ability to monitor data and individually tune cylinders.

Earnhardt-Childress Racing’s (ECR) engine shop builds these engines for its drivers and also leases engines to teams for more than $2 million a season. ECR typically works behind tightly sealed doors, but we were able to convince them to let us into its Welcome, North Carolina, facility to see what makes these 10,000-rpm small-blocks so powerful.

Built in a Box

The Chevrolet R07 is nothing like a traditional small-block. If you want to blame someone for that, blame Toyota. When Toyota entered NASCAR in the Camping World Truck series in 2004, and then Sprint Cup in 2007, it didn’t have a cam-in-block V8, so NASCAR allowed Toyota to build one from scratch.

Toyota showed up with something that looked like an F1 engine, NASCAR rejected it, and Toyota came back with a toned-down V8. Ford and Chevrolet -- who’d each been working on radical engine architectures of their own—saw this as an opportunity to have new designs pushed through the approval process.

5/19After Earnhardt-Childress Racing (ECR) receives a head from Chevrolet, it machines passageways inside that are then plugged with machined caps. Why not use those as extra water passageways? “Because air is lighter than water,” says Randolph. The old Chevy SB2 NASCAR engine paired its two inside exhaust ports side-by-side, causing a major hot spot that has been fixed with the R07.

In an attempt to put all three engines on equal footing, keep development costs in check, and make the engines relatable to the audience, NASCAR created what it called the “box.” This box is a list of more than 50 parameters that all Sprint Cup engines must adhere to. These parameters include the placement of the camshaft, bore spacing, and cylinder-head-port centers. The parameters meant teams could build new engines that wouldn’t need to be based on an OEM design or even look like one.

Block

Just like in the early years of NASCAR, you have the ability to purchase any part of this engine new. A division within the Advanced Engine Engineering Group at GM Powertrain produces and sells the R07 block and heads. The biggest advancements in the R07’s compacted-graphite-iron block are its internal passageways. Precision castings for the water jackets greatly improve water flow and cut down on hot spots found in the previous SB2. The distributor has been replaced by a cam-position sensor mounted in the front of the engine to eliminate possible camshaft twisting, which could potentially change the timing of the coil-near-plug ignition.

Cylinder numbering and firing order are traditional small-block Chevy, but the No. 2 cylinder is farther forward, in order to straighten out the intake runners. The oiling system has been retooled within the block, as well. The dry-sump oil pump cycles oil through separate channels that are divided between the top and bottom of the long-block.

10,000 RPM

Oil serves new purposes in the R07. “Now, we’re using the oil to cool and dampen parts, where back in the day it was only used as lubrication,” says Danny Lawrence, trackside manager at ECR Engines. “It’s become a major part in keeping the engine alive.” When the engine is running, oil fills the inside of the valve covers, completely submerging the valvesprings. There are level tubes built into the valve covers that drain the oil back through the block. The crew must drain this oil (via a metal release valve button on the back of the passenger side of the block, above the bellhousing), before removing the valve covers to work on the engine.

Weight and friction also play major factors in high-rpm operation. “Each piece is refined. We treat the engine as multiple units: the crank, the rods, and the pistons. How it’s all put together. Years and years of research and development to get the parts built to last 600, 700, or 800 miles without an issue,” says Lawrence. “It’s a piece of jewelry.” Most of the key rotating parts have minimum weight requirements, issued by NASCAR. For example, the intake valves are built from titanium and weigh right at the limit of 70 grams. “We are in a very tight box, but we try to massage everything within the rules.”

10/19ECR normally buys cranks from Superior Crankshaft (Pankl Engine Systems) or Bryant Racing, but does some top-secret work to them.

Expensive parts are only a piece of the puzzle when constructing a high-rpm, long-lasting race engine like this. “The major difference between our engines and street engines are the tolerances, coatings, and bearings,” says Randolph. The main advantages of the ECR program are its attention to detail and quality machine work. “Bearings are tight, with tolerances to within 0.0002 inch,” says Randolph. The R07 uses 2-inch-diameter main bearings and 1.850-inch-diameter rod bearings, per NASCAR rules.

NASCAR attempts to limit engine speed to 9,500 rpm by allowing only certain transmissions and final-drive gear ratios at different tracks, “but that’s hard to do because of weather and track conditions,” says Randolph. So if a car runs more than 9,500 rpm, it’s not necessarily a rule violation.

During the ’13 Kansas race, where Richard Childress Racing’s (RCRracing.com) Kevin Harvick won, his car operated around 9,500 rpm. Restrictor plates cut power almost in half, which left RCR’s engines running at 9,000 rpm for the ’13 Talladega race. At Martinsville, the weekend after this article was written, RCR will see 9,900 to 10,000 rpm “all day long,” says Lawrence.

Induction

The induction system is easy for anyone to obtain, as companies such as Summit Racing keep them in stock. Edelbrock’s R07 high-rise intake retails for $629.97, and Holley Performance’s billet throttle body retails for $2,500. These are the exact parts that NASCAR teams purchase -- not watered-down versions.

Before fuel injection was fitted to the R07, there were roughly five intake manifolds to choose from. Currently, NASCAR allows one from the OEM (Chevrolet Performance’s PN 751) for restrictor-plate racing and the one from Edelbrock (PN 2837) for all other tracks. “Intake manifolds used to be hand-whittled. Now the teams have CNC machines, and these castings have the ability to be tuned for different track applications,” says Rod Sokoloski, designer and NASCAR program manager with Edelbrock. Teams buy rough manifolds that weigh around 30 pounds and internally port them, removing up to 12 pounds. The intakes fall within NASCAR’s box of limitations, the most important rule being no altering the outside, especially injector placement.

11/19The R07 has cooling and oiling properties that make it more advanced than a traditional small-block.

The Switch to Fuel Injection

The fuel-injection learning curve has been drastic for teams, but the pay off has proven to be worth it. “We can view a lot of data that we’ve never been able to before. We can see where we are getting beat in practice and overlay data with video,” says Lawrence. But NASCAR “still wanted to keep the strategy there.” There are no fuel-level sensors, and only the minimum amount of data is accessible by the teams because part of the engine control unit (ECU) is blocked. “NASCAR [rule enforcers have] much more data collection than us. They have people looking at the data just like we do,” says Randolph. NASCAR monitors the data it collects, looking for any standouts that would cause further investigation into potential cheating.

Your typical production EFI system may be more advanced than NASCAR’s, despite the price difference. Generally, factory fuel-injected engines place the injectors as close to the intake valves as possible, and originally NASCAR planned to allow teams to determine their own injector layout.

“If they left it up to us, we would spend a lot of money to find the ideal [injector] placement. The more you move [the injectors], the more they may favor one manufacturer’s engine over another,” says Chevrolet’s Pat Suhy. NASCAR ultimately mandated the injectors be moved up into the runners, leveling the playing field for all. “[The injector location] was badly sub-optimized,” but it was bad for everyone rather than good for one manufacturer.

Since 1969, all NASCAR Cup cars have featured Holley carburetors, but when NASCAR decided to switch to EFI, Holley wasn’t the only company to throw its hat in the ring. “We wanted to stay on the engine,” says Senior Design Engineer James Dralle with Holley Performance. NASCAR wanted the transition to be effortless, retaining the same air box, intake, and restrictor plate (denying Holley’s design for an internal choke, which could have served the same function as a restrictor plate). NASCAR required the throttle body to have a physical throttle stop and retain the same inlet shape as the carburetor.

The traditional NASCAR 830-series Holley four-barrel featured 1.591-inch-diameter venturis, and the new EFI throttle body uses smaller venturis that measure 1.375 inches each. This reduction was an effort to keep teams from making significant power gains with EFI. “There are times during full-throttle dyno pulls where you can get more power from a carb than with EFI, but the difference with engine performance is outweighed by the tune-ability and consistency of the EFI,” says Dralle. During races it’s thought that lateral loads push gas around inside the carburetor, which causes inconsistency; with EFI, what’s happening on the track is much closer to what’s happening on the dyno.

The major incentive to EFI is the ability to individually tune each port. “We treat it like eight individual engines that share a common crankshaft,” says Randolph. This has allowed teams to make slightly more power, but they won’t say exactly how much.

McLaren Electronic Systems builds the ECUs for NASCAR and issues the partly sealed TAG-400N speed-density fuel-management system ECUs to Sprint Cup teams. These ECUs use a coolant-temperature sensor, cam- and crank-position sensors, a throttle-position sensor (TPS), manifold-absolute-pressure (MAP) sensor, and two oxygen (O2) sensors mounted in the header collectors to control how the engines run. The speed-density system uses the throttle position, engine speed, and intake manifold pressure to determine the fuel curve used. If the throttle-position sensor fails, the engine can also run using just the engine speed and MAP sensor info as a failsafe. The system is always sequential fire, no matter the rpm.

18/19This engine is heading to Dover, but ECR uses four different engine packages throughout a given season. These packages are Super Speedway (Talladega, Daytona), Speedway (California, Michigan), Mid-track (Charlotte), and Short Track/Road Course (Martinsville, Bristol). Each package is designed to move the torque curve around through changing the cam, cylinder head, headers, and intake design.

The Future

The week this article was written, NASCAR approved Toyota’s new engine, and Chevrolet had its next engine design turned down. “Now we’ve learned, and next year we’ll get it [approved], but it’ll be different,” says Lawrence. “Only three people at RCR have seen [the new] engine.”

Chevrolet and ECR may not actually be disappointed that Toyota’s engine was approved. Now they’ll get to see what advancements Toyota has made before they resubmit their engine to NASCAR in September 2014.

19/19Next year, the teams anticipate an upgrade to a stronger 140-amp alternator to aid with additional electric cooling motors for the drivers. That means an extra rib on the serpentine belt, which will rob 5 hp. Sometimes during qualifying, teams will cut the power steering and alternator belts off to gain that little bit more.

With street-car advancements like direct injection and turbos becoming more common, it begs the question if NASCAR will follow suit. “Part of NASCAR’s dilemma is defining the next-generation engine,” says Suhy. The team at ECR sees a strong relationship between NASCAR and the manufacturers. “There will be direct injection in the next five years. I’m guessing there to be some downsizing and boosting, as well, like you see in production cars,” says Randolph.

But turbos and V6 aren’t as all-American as the 58-year-proven pushrod V8. Will NASCAR be able to sell a turbo V6 to the audience of this sport? “What kind of noise would that new engine need to make? Make a V6 sound like a V8? Sexy race-engine noise?” says Suhy. Randolph added, “Certainly noise quality, pitch, that’s always going to be a part of the conversation, but it’ll come down to NASCAR asking the manufacturers, ‘This is your theater for your products; where do you want to see it go?’”